In the related art, an electrode assembly is assembled by stacking a plurality of C-type or A-type bi-cells, each of the C-type or A-type bi-cells including electrodes having the same polarity and an electrode having a different polarity and disposed between the electrodes of the same polarity.
Referring to FIG. 1, an electrode assembly 1 having stepped portions may be assembled as follows: a first electrode stack is formed by stacking a plurality of bi-cells having the same area such as an A-type bi-cell 13 and a C-type bi-cell 11 shown in FIG. 2; and a second electrode stack in which bi-cells having equal areas smaller than the area of each electrode of the first electrode stack is disposed on the first electrode stack. In this manner, a stepped electrode assembly having an area decreasing in a vertical direction, such as the electrode assembly 1 shown in FIG. 1, may be assembled.